Fiction writers often create elaborate imaginary kingdoms or galactic empires, ruled by iron-fisted dictators or feckless legislatures or councils of wise elders. Often, however, the politics of such regimes often falls flat. Powerful figures line up for or against the protagonists seemingly at random, or “because the author says so.” While this can be fine, depending on the main emphasis of your story, it would be better to understand the dynamics of political conflict in your imaginary regime, so that you can use it as a basis for creating a compelling story.

But there are many different kinds of regimes: democracies, dictatorships, aristocracies, each of which has innumerable flavors and nuances in their structures. Does an author need to become an expert in all of them to write good political conflict?

Not necessarily. A good starting point would be a general theory of how regime leaders stay in power or get overthrown—simple enough to be easily applied to your story, flexible enough to be relevant to ancient kingdoms, modern democracies, and everything in between. Fortunately, there is such a theory, developed by Bruce Bueno de Mesquita and his collaborators, and known in comparative politics as selectorate theory. It goes like this:

Imagine a Kingdom of Crelia. Its king, Rothgar the VIII, rules over a strong aristocracy headed by nine barons, not all of whom like him very much, and a much larger pool of powerless peasants who pretty much have to suffer whatever comes. Rothgar doesn’t have to worry much about what the peasants think; but he must pay attention to the barons, because if enough of them turned against him, Rothgar could be overthrown and beheaded. Fortunately, he doesn’t have to keep all of them happy all the time—just a fraction of them, let’s say four. Their strength, plus his own, are enough to keep the other five barons in check.

To keep his supporters happy, therefore, King Rothgar keeps their taxes somewhat lower than the other five barons, gives them more privileges at court, and sets royal policy to favor their interests over those of the five other barons, to some degree. (The peasants, needless to say, get milked for all that Rothgar and the barons can get.)

In terms of selectorate theory, the peasants (Residents) have no role in choosing the king. The nine barons, on the other hand, make up the Selectorate—the group of people with the right, or the power, to influence the selection of king. The selectorate is the outer circle; the inner circle, on the other hand, is the Winning Coalition, the four barons who make up Rothgar’s chief supporters.

Rothgar’s survival depends on maintaining his winning coalition. But he need not keep it as the same four barons; indeed, his main leverage over them is the threat of replacing a pushy baron with one of the other five barons in the selectorate. That threat allows him to keep the expense of maintaining his allies down to a reasonable level, so he can keep more taxes to himself.

His threat would be even more effective if he could expand the size of the selectorate, by appointing five or six peasants to the nobility. Now, there are fifteen barons total, and the king still needs only four of them as his supporters. With so many more options to choose from, Rothgar need pay a much lower price to secure his base of support. Any baron that tries to hold out will quickly be replaced by a more cooperative rival.

However, suppose that there are not nine total barons but only six. Then, each of the four supporter barons is in a powerful position; the king will have a much harder time replacing them individually, and has no way to replace them all. They can then extort a heavy price for their support, perhaps so heavy that the king’s own revenue is squeezed and he loses power over time. The same would be true if the king suddenly needed seven barons out of nine, instead of just four. (The country, needless to say, will suffer as spending on public goods drops off a cliff.)

As a rule, if the winning coalition is large relative to the size of the selectorate, it can extort a high price. If it is small relative to the selectorate, the ruler can keep more revenue for himself. At the limit, if you make the entire populace part of the selectorate while only requiring a tiny winning coalition (for example, with a strict meritocracy or an authoritarian party-based regime), then your supporters will have to make do with meager benefits indeed.

In general, therefore, the ruler has an interest in expanding the selectorate to cover a larger part of the population, and the selectorate members have an interest in restricting its size. Likewise, the ruler has an interest in reducing the necessary size of the winning coalition, and the selectorate would want to increase the size of the winning coalition.

You can see these dynamics play out in the political struggles over extending the right to vote. In the United States, for example, it was originally the case that only property-owning freemen could vote, about 6% of the population. Government policy thus tended to favor the landowning class. Over time, the right to vote was slowly extended to most white men, then most men, then most adults. At each step, some who already had the vote feared that their interests would be harmed by the new voters, and fought bitterly against their inclusion. And at each step, the size of the winning coalition grew along with that of the selectorate, and government policy thus changed to benefit larger portions of the total populace.

This brings up an important point. When the winning coalition is small, it can be bought off with policies that benefit itself, even if those policies harm the populace at large (as they often do; it is easy to tax the populace and enrich a handful of supporters). But as the winning coalition grows, relative to the populace as a whole, it becomes more likely that policies benefiting the winning coalition will also benefit the populace in general.

This, argues selectorate theory, is the main reason that democracies tend to be better run (on average) than dictatorships—the ruler must set policies that benefit 50% of active voters at a minimum, instead of a small handful of powerful nobles, generals, or businessmen.

The model can fit any regime you imagine. Communism? The Communist Party membership was quite large, compared to the size of the Politburo; regime figures could be replaced easily, and often were. Banana republic? The key figures are the generals and the main business leaders, who are hard to replace and thus demand a high price for their support. (For more, read The Dictator’s Handbook.)

How can you use this in your fiction? Selectorate theory gives you several points of conflict to focus on: expanding or shrinking the winning coalition, or the selectorate; exactly who gets to be in the winning coalition; policies that benefit the winning coalition and harm the rest of the country, or an effort to change such policies as winning coalitions shift; a ruler who allows his winning coalition to fall apart, so a challenger can assemble such a coalition of her own. You can tune the details to fit your particular setting; but selectorate theory gives you a strong foundation on which to build the political conflict in your story.